Currently, the most ubiquitous cellular communication system is the 2nd generation communication system known as the Global System for Mobile communication (GSM). Further description of the GSM TDMA communication system can be found in ‘The GSM System for Mobile Communications’ by Michel Mouly and Marie Bernadette Pautet, Bay Foreign Language Books, 1992, ISBN 2950719007.
To further enhance the services and performance of the GSM communication system, a number of enhancements and additions have been introduced to the GSM communication system over the years.
One such enhancement is the General Packet Radio System (GPRS), which is a system developed for enabling packet data based communication in a GSM communication system. Thus, the GPRS system is compatible with the GSM (voice) system and provides a number of additional services including provision of packet data communication, which augments and complements the circuit switched communication of a traditional communication system. Furthermore, the packet based data communication may also support packet based speech services. The GPRS system has been standardised as an add-on to an existing GSM communication system, and can be introduced to an existing GSM communication system by introducing new network elements. Specifically, a number of Serving GPRS Support Nodes (SGSN) and Gateway GPRS Support Nodes (GGSN) may be introduced to provide a packet based fixed network communication.
3rd generation systems are currently being rolled out to further enhance the communication services provided to mobile users. One such system is the Universal Mobile Telecommunication System (UMTS), which is currently being deployed. Further description of CDMA and specifically of the Wideband CDMA (WCDMA) mode of UMTS can be found in ‘WCDMA for UMTS’, Harri Holma (editor), Antti Toskala (Editor), Wiley & Sons, 2001, ISBN 0471486876. The core network of UMTS is built on the use of SGSNs and GGSNs thereby providing commonality with GPRS.
Cellular communication systems generally support services by the creation and allocation of logical and physical radio bearers. For example, radio bearers may be set up in support of signalling and user data communications for a given service provided to a user equipment.
Specifically, UMTS and GPRS operate with the concept of Radio Access Bearers (RAB) which provide a communication connection from the user equipments to the core network.
These RABs may either be UMTS signalling plane RABs which support UMTS signalling information or can be UMTS user plane RABs which support user data traffic. In UMTS, the UMTS signalling plane RABs support standardised UMTS signalling data required by the operation and management of the UMTS system. For example, mobility management and call control is supported by signalling using UMTS signalling plane RABs. In contrast, the UMTS user plane RABs provide a bearer which can be freely used for any data by the specific service. Thus, the data transmitted on UMTS user plane RABs is independent of the UMTS cellular communication system and can be used by the application in any suitable way (the UMTS user plane RAB can be considered a bit pipe for the user data of the service).
In some systems, such as UMTS, a given user equipment or service can be supported by a UMTS signalling plane RAB and one or more UMTS user plane RABs. The UMTS signalling plane RAB is used to control and manage the service by the UMTS cellular communication system. The UMTS user plane RABs are used exclusively by the service and the plurality of UMTS user plane RABs can for example be used for different data types supporting the same communication, e.g. one bearer may be used for video communication and another for audio communication. Furthermore, for many services, additional signalling is required between e.g. a server and an application running on the user equipment. In such cases, a UMTS user plane RAB can be allocated specifically to support this signalling whereas another UMTS user plane RAB can be used for the application user data itself. Thus, the UMTS user plane RABs for a given service can be divided into one or more service signalling plane RABs and one or more service user plane RABs.
Specifically, a service known as IMS (IP Multimedia Subsystem) is developed for allowing efficient Multimedia Internet access for user equipments of a UMTS cellular communication system. In order to set up an IMS service, a minimum of one UMTS signalling plane RAB and two UMTS user plane RABs are required. The UMTS signalling plane RAB supports the required UMTS signalling whereas one UMTS user plane RAB is used as an IMS signalling plane RAB that supports the signalling for the IMS service and another UMTS user plane RAB is used as an IMS user plane RAB for communicating the user data.
However, although the use of multiple UMTS user plane RABs provides a flexible system for supporting different aspects of a given service, it also tends to result in a complex and inefficient management of the radio bearers and the air interface resource. Specifically, each UMTS user plane RAB is managed and controlled individually resulting in complex procedures for setting up and terminating a service using a plurality of UMTS user plane RABs. It also tends to result in an inefficient management and in a system which is sensitive to errors or fault conditions.
Hence, an improved radio bearer management would be advantageous and in particular radio bearer management allowing increased flexibility, improved efficiency, facilitated radio bearer management and/or improved radio bearer management would be advantageous.